Field of the Disclosure
The present subject matter relates to radio frequency identification (“RFID”) devices. More particularly, the present subject matter relates to systems and methods for testing RFID straps using an oscillator.
Description of Related Art
RFID tags and labels (collectively referred to herein as “devices”) are widely used to associate an object with an identification code. RFID devices generally have a combination of antennae and analog and/or digital electronics, which may include, for example, communications electronics, data memory, and control logic. For example, RFID tags are used in conjunction with security locks in cars, for access control to buildings, and for tracking inventory and parcels. Some examples of RFID tags and labels appear in U.S. Pat. Nos. 6,107,920; 6,206,292; and 6,262,692, all of which are hereby incorporated herein by reference in their entireties.
One difficulty associated with RFID devices is the need to test operation of such devices as part of the manufacturing or fabrication process. In fabrication of RFID devices, the devices may be formed on a sheet or roll or web of material, closely spaced apart. In traditional methods of activating, reading, and/or detecting RFID devices, an antenna is used to send radio frequency (“RE”) fields over a relatively long range, that is, over intervening free space. When such methods are applied to testing closely spaced RFID devices, it is difficult to test a single RFID device, since the RF field interacts with several devices simultaneously, and the various RFID devices may interact with one another.
According to other known test methods, an RFID device is integrated into a bridge or other structure, with parameters such as voltage and current being monitored against time. However, such methods are not well-suited to characterization of high frequency parameters, such as the input of an RFID chip, or with a capacitance on the order of 1 pF, or at frequencies between approximately 700 MHz and 1 GHz. Still other test methods involve making a frequency selective network that incorporates an RFID device and then determining the resonant frequency by sweeping a known source across a band, but such methods may be relatively slow (e.g., on the order of milliseconds).